The in vitro cell culture of resting lymphoid cells from normal mice with either Interleukin-2 (IL-2) or Interleukin-4 (IL-4) has been shown to generate populations of lymphoid cells which are cytotoxic to tumor cells. These cells are generally referred to as lymphokine-activated killer (LAK) cells. IL-2 and IL-4 are distinct T cell derived cytokines or, more particularly, lymphokines. Both IL-2 and IL-4 have been shown to have some overlapping activities. For example, IL-2 was initially identified as a T cell growth factor, but has since been shown to bind to and promote propagation or function of such diverse cell types as B cells, monocytes, epidermal Langerhans cells, oligodendroglial cells and NK cells. Moreover, IL-4 was originally thought to function primarily by inducing B cell proliferation and maturation, IL-4 has since been shown to interact with hematopoietic stem cells, macrophages, mast cells, and T cells.
Mammalian Interleukin-7 (IL-7) had been previously designated lymphopoietin-1. The cloning and expression of human and mouse IL-7 has been described in U.S. Pat. No. 4,965,195 and the disclosure of which is incorporated by reference herein. Interleukin-7 is a lymphopoietic growth factor that was first isolated and cloned by virtue of its ability to stimulate the growth of B and T cell progenitors in bone marrow. Published PCT Application WO89/03884 (May 5, 1989) and EP-A-0314415 (May 3, 1989) refer to DNAs, vectors, and related processes for producing mammalian IL-7 polypeptides by recombinant DNA technology. The relevant disclosures of these published patent applications are incorporated by reference herein. The cloning of murine IL-7 was first reported in the scientific literature by Namen et al., Nature 333:571 (1988) and human IL-7 by Goodwin et al., Proc. Natl. Acad. Sci. USA 86:302 (1989). Purification of murine IL-7 from supernatants of transformed bone marrow stromal cell lines indicated an apparent molecular weight of approximately 25,000 daltons (see, for example, Namen et al., J. Exp. Med. 167:988 (1988)). The cloned DNAs reported by Namen et al. and Goodwin et al. suggest minimum molecular weights for the murine and human IL-7 polypeptides of 14,897 and 17,387 daltons, respectively, exclusive of any glycosylation.
Cloning, characterization and expression of sufficient quantities of IL-7 has provided sufficient recombinant polypeptide to begin characterizing its spectrum of its biological activities. IL-7 was originally defined by its ability to stimulate the proliferation of pre-B cells (B220.sup.+) derived from long-term bone marrow culture (see, Whitlock et al., J. Immunol. Methods 67:353-69 (1984)). IL-7 was unable, however, to stimulate the proliferation of mature B cells or to induce the differentiation of pre-B cells to surface Ig.sup.+ cells (Lee et al., J. Immunol. 142:3875-83 (1989)).
More recent references have shown that T cell lineage cells respond to IL-7. For example, resting fetal and adult thymocytes of most surface phenotypes proliferate in response to IL-7 in a manner independent of IL-2, IL-4, or IL-6 (Conlon et al., Blood 74:1368-73 (1989)). Further, mature peripheral T cells respond to IL-7 in the presence of suboptimal mitogen concentrations (Chazen et al., Proc. Natl. Acad. Sci. USA 86:5923-27 (1989)). Morrissey et al., J. Exp. Med. 169:707-16 (1989) have shown that IL-7 can provide a costimulatory signal for the in vitro proliferative response of purified murine T cells to CON A by inducing IL-2 production. Additionally, Chazen et al., Proc. Natl. Acad. Sci. USA 86:5923-27 (1989) have further shown that IL-7 in combination with PMA, can directly stimulate T cell activation without intervention by another cytokine messenger. Response to a combination of IL-7 and PMA was not inhibited by high concentrations of neutralizing antibodies to either IL-2 or IL-4 and was largely resistant to immunosuppressive effects of CsA, a drug which inhibits the transcription of a number of lymphokine genes, including those encoding IL-2, IL-4 and interferon-.gamma..
A wide spectrum of murine cell lines and primary cell lines display IL-7 receptors. These cell lines include cells of both lymphoid and myeloid origin. Therefore, the cytokine IL-7 has the potential for a wide range of activities on a wide variety of cell types.
The differentiation of lymphoid lineage cells involves a complex and as yet poorly understood series of events. Although a common precursor, or stem cell, is believed to give rise to both B and T lymphocytes, the steps involved in the differentiation process have remained elusive. Early CD4.sup.- /CD8.sup.- thymocytes can repopulate the thymus of irradiated recipients and differentiate into various thymocyte subpopulations. It is not known what factors are involved in the differentiation process.
Conlon et al., Blood 74:1368-73 (1989) refers to a proliferative response of murine thymocytes to murine IL-7. IL-7 alone was mitogenic for thymocytes and further augmented an IL-7 response with CON A. Conlon et al. further demonstrated that IL-7 stimulated the proliferation of CD4.sup.- /CD8.sup.- cells that represent what is believed to be the least differentiated thymocyte subpopulation. Moreover, the response of thymocytes to IL-7 did not appear to be due to the production of other known T cell growth factors, such as IL-2 and IL-4. This IL-7 activity is in contrast to other lymphokine activities, such as IL-1 or IL-6, which have been shown to enhance T cell responsiveness by either the production of IL-2, IL-4, or by upregulation of the IL-2 receptor, or both.
The technique of adoptive immunotherapy and its various modifications are described, for example, in Rosenberg, Scientific American, pp. 62-69 (May, 1990). The adoptive immunotherapy model was first developed using IL-2. The procedure was developed in mice. Briefly, one first removes the spleen from a healthy syngeneic mouse, isolates the lymphocytes and cultures the isolated lymphocytes in a culture medium containing IL-2. IL-2 induces certain lymphoid cells and NK cells in culture to become cytolytic and tumorcidal. The activated lymphocytes and IL-2 are injected into tumor-bearing mice as a method of immunotherapy of cancer. Human clinical studies have isolated lymphocytes from whole blood of the patient, activated the lymphocytes in culture with IL-2 to induce LAK activity, and treated the patients with about 50 billion LAK cells infused intravenously together with human IL-2. Various clinical studies found the necessity of infusing IL-2 together with the activated lymphocytes.
Rosenberg and his colleagues have attempted to treat various cancers with activated LAK cells in combination with IL-2 and with IL-2 administered alone. Their results to date have shown complete cancer remission in 14 of 177 patients with the combination of activated LAK cells plus IL-2 and in 4 of 130 cancers with IL-2 alone. When partial remission cases are considered, 25% of the patients who received activated LAK cells plus IL-2 improved and 17% of the patients who received IL-2 alone improved. These studies are ongoing.
There have been reported side effects with the adoptive immunotherapy technique with lymphocytes activated by IL-2 and administered concomitantly with IL-2. The side effects include proliferation of lymphocytes in tissues that interfere with the function of vital organs. Administration of IL-2 leads to leakage of fluid from blood into tissues with resultant weight gain.
Therefore, there is a need in the art to better characterize the precise physiologic and immunologic functions of IL-7 polypeptides. There is a further need in the art to improve upon immunotherapeutic techniques with different cytokines under different exposure conditions, different combinations and different pharmacokinetics parameters. This invention was made in an effort to find an optimal immunotherapeutic use for IL-7 polypeptides alone or in combination with other cytokines or other factors.